1. Field of the Invention
The present invention relates generally to the field of display panels, and more specifically, to an apparatus and method for allowing display modules to communicate information about themselves to other display modules in the same display panel.
2. Description of the Related Art
Most electronic signs or display panels today are based on a modular construction, that is, they are comprised of a plurality of display modules. LED is the dominant technology used in full-color outdoor display panels; however, there are other types of display technologies—such as plasma, LCD (liquid crystal display) and CRT (cathode ray tube)—that are also based on a modular design. The challenge with any of these modular display panels is ascertaining where each module is relative to the other modules so that the controller can send the appropriate video data to the correct module.
Existing methods of dealing with this problem include the use of: (1) specific cabling; (2) daisy chain cabling; (3) module address switch; (4) module address programming; and (5) a software configuration file. Each of these methods, and its shortcomings, is discussed below.
The problem with specific cabling is that each module has to have its own special cable. A burden is therefore placed upon the installer to connect each module to its specific cable. In large display panels with hundreds of cables, wiring errors are common and difficult to find and correct.
With daisy chain cabling, the controller is connected to the first module, which is connected to the second module, which is connected to the third module, etc. Daisy chain cabling is not very flexible and requires specific cabinet layouts. Often times cabinet designs or display panel configurations are not optimal for the number of modules on a chain, requiring additional controllers. Another problem with daisy chain cabling is that if a module fails, all other modules connected to it downstream will also lose data, causing a large portion of the display panel to fail when only one module has failed. Furthermore, daisy chaining modules creates electrical signal integrity problems since a large amount of data must pass through each module to get to the next one.
Another method for solving the problem of ascertaining where each display module is located relative to other display modules is to associate a switch (preferably a DIP (dual in-line package) or rotary switch) with each module. Each switch is uniquely set for each module by a technician. The switch settings must be correctly set in order to identify the position of the module in the display panel, and the setting typically constitutes a row and column assignment. The problem with this method is that the burden for correctly setting the switches falls on the installer. With large display panels consisting of hundreds of modules, this can be a tedious and error prone method of configuring the display panel. Furthermore, it is time-consuming.
Yet another method for solving the problem of mapping displaying modules on a display panel is to use module address programming. Module address programming involves programming each module with an external device or via a control panel physically located on the module itself. This method is obviously labor-intensive and prone to human error.
Finally, a software configuration file can be used to map the location of display modules on a display panel. This method assigns to each module its own unique address, which is usually programmed at the factory. A technician then enters these addresses into a software configuration file, and a main controller reads the software configuration file to generate a lookup table to determine the coordinate location of each module.
Although manual creation of the controller software configuration file works, it can take a single technician two to three hours to fully populate the configuration file with coordinates and corresponding display module addresses before the display panel can be tested and installed. As the overall dimensions of the display panel increase, the size of the configuration file must also increase; some larger display panels require over 2000 separate entries in the configuration file. Due to the sheer number of entries and the potential complexity of the display module addressing scheme, manual entry of display module addresses and coordinates is prone to error. If a single character is transposed or typed incorrectly in a module address or x-y coordinate, the display panel will display image information incorrectly. Debugging these errors is difficult and time-consuming, often requiring a technician to repeat the same process he or she used to create the configuration file in the first place.
If the process of creating the configuration file is cumbersome, maintenance of the configuration file after the display panel has been installed can be equally complicated. When an LED display module fails, an electrician or other sign technician must manually replace it. Because each display module has its own unique address, the technician must update the configuration file to match existing display panel coordinates with the address of the new display module. This means the technician must manually record the address of the old and new circuit boards while in the field, and then gain access to the controller software's configuration file to replace the address of the old display module with the address of the new one. This manual process is susceptible to recording or input error and is complicated by the fact that the individual replacing the display module in the field may not have either the computer expertise or the physical access to the controller software to update the configuration file successfully.
What is needed is an automated method to populate the configuration file of the display panel's controller software with the identifiers and associated x-y coordinates of each display module in the display panel. Such a solution would eliminate the manual steps required to create the controller software configuration file, both when populating it before installation of the display panel and when updating it during maintenance following deployment.